Acoustic Data Compression for MWD LWD Telemetry
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Solution Overview
Problem
Acoustic logging data processing and analysis techniques face challenges in transmitting detailed acoustic data from downhole LWD systems to the surface due to bandwidth constraints, leading to sub-optimal decisions in wellbore steering and completion techniques due to lossy compression techniques.
Innovation Solution
A novel compression technique that transmits velocity values and coherence data for the first three peaks of semblance projections, allowing for accurate reconstruction of velocity curves as a function of depth, reducing data loss and maintaining information integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lossy compression techniques are used to reduce data transmission requirements, then data transmission bandwidth is reduced, but data integrity and information quality deteriorate
Solution Approach 1:
The patent extracts and transmits only the most critical features from the full acoustic dataset - specifically the velocity values and coherence data corresponding to the first three peaks in semblance projections. This selective extraction maintains data quality for the most important information while dramatically reducing the total data volume that needs to be transmitted through bandwidth-constrained telemetry channels.
Solution Approach 2:
The patent transforms the acoustic data from its original raw form into processed parameters (velocity values and coherence data) that capture the essential formation characteristics. By changing the data representation from complete waveforms to extracted velocity-coherence pairs, the system reduces transmission requirements while preserving the information needed for accurate formation evaluation and velocity curve reconstruction.
2Loss of information
If more acoustic data is transmitted to the surface, then information quality improves, but data transmission bandwidth requirements increase
Solution Approach 1:
The patent segments the acoustic data transmission into two components: velocity values and coherence data. This segmentation allows the system to transmit only the essential parameters needed for formation evaluation rather than the complete acoustic dataset, optimizing the balance between information quality and transmission volume for bandwidth-constrained LWD applications.
3Quantity of substance
If data processing is performed downhole to reduce transmission data, then transmission bandwidth is reduced, but processing complexity increases
Solution Approach 1:
The patent performs preliminary processing downhole by calculating velocity values and coherence data from the acoustic signals before transmission. This preliminary action extracts the essential features needed for formation evaluation, reducing the data volume for transmission while maintaining information quality. The processing is performed at the source using the LWD tool's computational capabilities, optimizing the trade-off between downhole processing complexity and transmission requirements.
Data Source
AI summary
Acoustic data acquired in a MWD/LWD system can be compressed for transmission to the surface. The compression technique can include semblance processing acoustic signals received at a plurality of receivers spaced apart from a transmitter to generate a semblance projection at each of a plurality of depths. Peaks of the semblance projection can then be telemetered to the surface, with each peak including a slowness (velocity) value and a coherence (semblance) value. The telemetered values may be processed at the surface to generate logs as a function of depth.